Prior to the instant invention, when a subscriber of a particular telephone service provider, as for example a long distance carrier in the United States, were to travel to a foreign country such as for example Canada, if the subscriber wants to use a telephone card issued to him from his telephone service provider to make a special service call, such as for example an operator assisted call, he would hear a message from the local telephone service provider where he was placing the call that his telephone card could not be used. This is because the local telephone service provider has no means by which to check whether the account number entered by the subscriber is a valid number, as the database in which valid numbers (or invalid numbers) are stored for comparing with the subscriber's calling card number can only be accessed by the subscriber's telephone service provider. One of the reasons that there was no interaction between the different telephone service providers was that each telephone service provider may be using a different type of signaling protocol.
There is prior art dealing with the conversion of different protocols. For example, in U.S. Pat. No. 5,182,748, there is disclosed a converter for converting an X.25 protocol to an X.32 protocol. However, this protocol conversion system does not deal with validation, but rather deals with coupling an X.25 terminal apparatus to a conventional telephone network, an ISDN, or a PBX system.
Another network communication system that utilizes conversion of protocols is disclosed in U.S. Pat. No. 5,377,191. There, a CCITT X.400 protocol is converted to an X.25 protocol. This conversion system is intended to be utilized by PTTs (postal, telegraph and telephone) authorities.
There also exists in the prior art a system whereby if a subscriber of a particular telephone service provider were to place a call (using his calling card issued by his telephone service provider) from an area serviced by another telephone service provider, he could only make the call back to the area serviced by his own telephone service provider. Thus, the subscriber is not able to place calls to a destination that may only be a short distance from the call origination location if the telephone service for the destination is provided by a service provider other than the one that he subscribes to. To overcome this inefficiency, the subscriber may dial a 1-800 number provided to him by his telephone service provider to reach an operator of the service provider. The operator may then be able to connect the call placed by the subscriber. However, this method is time consuming and takes up a lot of the capacity of the communications network insofar as the entire call needs to be routed to the operator of the telephone service provider of the subscriber.